A track joint is customarily held together by an interference fit between the ends of the track pins and their respective link bores into which the pin ends are tightly received. Even though a very high press force, varying from 60 to 150 tons depending on track size, is typically used to press the links onto their respective pin ends, the links still have a tendency to move outwardly on the pin as a result of working forces exerted on the track during operation of the vehicle. This outward movement causes the joints to become loose or develop what is frequently referred to as end play.
Until recently, the amount of end play which developed in operation was normally within acceptable limits and was not critical to the operation of the track. However, with the introduction of larger crawler vehicles and engines with greater horsepower, even for smaller vehicles, the amount of end play has increased so as to become a concern, especially for sealed and lubricated track. In sealed and lubricated track, excessive end play can lead to a loss of the lubricant and the ingress of abrasive materials which can lead to excessive wear and premature failure of the track.
Various methods have been employed to limit the amount of end play in track joints. Keeper assemblies, such as those disclosed in U.S. Pat. No. 4,182,578 issued on Jan. 8, 1980 and U.S. Pat. No. 4,288,172 issued on Sept. 8, 1981, both to Richard E. Livesay et al. and both assigned to the assignee hereof, have been successfully employed to reduce such end play movement. In order to accommodate manufacturing tolerances, joints utilizing such keepers must have a certain amount of clearance which produces a limited amount of built-in end play. As a result, these keepers reduce, but do not completely eliminate, end play.
Another method of limiting end play is disclosed in U.S. Pat. No. 3,831,257 issued to Roger L. Boggs et al. on Aug. 27, 1974, which patent is also assigned to the assignee hereof, wherein welding about the ends of the track pins is employed. In this method, retention is quite dependent on the strength of the weld. In practice, weld strength is difficult to control with any degree of consistency. If a weld is so weak that it breaks, all of its retention ability is lost.
In U.S. Pat. No. 1,507,757 issued to Edwin H. Savage on Sept. 9, 1924, a soft metal key is driven through an opening in a rail and shoe of a track unit and into an angled pin groove to provide a locking device for securing the pin with the track unit.